Shares in Sarepta Therapeutics SRPT, already the best-performing biotech stock of the past 52 weeks, rose 13% in pre-market trading after the company announced that it plans to submit its muscular dystrophy drug, eteplirsen, to the Food and Drug Administration in the first half of 2014. The decision comes after a series of discussions between Sarepta’s management team and the FDA, and is likely to be taken as a sign that the drug could be approved. Eteplirsen showed dramatic results in a 12 patient trial earlier this year, with boys who had Duchenne muscular dystrophy actually showing temporary improvement then slowed decline in the distance they could walk in six minutes.